Most contemporary learning theorists describe conditioning in terms of the acquisition of associations between internal representations of the conditioned stimulus (CS) and the unconditioned stimulus (US). These associations allow presentation of the CS to activate the US representation, so that the CS can substitute for the US in a variety of behavioral, emotional, and cognitive functions originally controlled by the US alone. The proposed research would explore the nature and function of CS-evoked event representations, especially their ability to activate perceptual or memorial images of the US, allowing the formation of new associations with that US, even in its absence. The research would determine the conditions under which various functions of CS-activated event representations are displayed, and would explore a number of limitations on those functions. Although the proposed research is primarily intended to address questions about fundamental behavioral properties of learning and memory, it also has clinical relevance For example, food aversions mediated by evoked cognitive images rather than physical illness may contribute to eating disorders. Similarly, implicitly conditioned imagery may contribute to the establishment and display of inappropriate emotional behavior in some cases of anxiety and reaction to trauma. Likewise, many clinical therapeutic treatments involve patients' use of techniques of imagery in which activation of images of emotionally significant events is placed under the control of explicit prompts through conditioning-like procedures. The proposed research provides a basis for the understanding of basic processing of imaginal events in associative learning.